A number of different arrangements for the addition of water to electrochemical accumulator batteries are already known. A common feature of these is that each cell has devices which permit the supply of water to a predetermined maximum level. The function of these devices can be based on ghe hydrostatic effect or on floats in different variants. The devices are attached in series or parallel connection to a storage container for water.
The systems differ primarily with regard to the arrangement of the supply of water to the level-controlling devices. This object may appear trival, although in practice it has proved difficult to resolve with regard to the requirement for flexibility of the design and low cost. A suitable system should, in fact, be capable of being applied to:
batteries with cells positioned in groups on different planes, such as in a stepped frame, on shelves positioned vertically beneath one another, or on an inclined plane, such as a floor which slopes towards a floor drainage channel;
battery installations in a concealed or not easily accessible position, such as in railway wagons and diesel locomotives, etc.;
batteries whose cell enclosures can exhibit considerable differences in respect of their material, construction and thus even their sensitiveness to pressure, for which reason the applied positive or negative pressure should be small, so that the capacity of the container is not affected to any significant degree or the risk of fracture is eliminated; consequently, any series of level-controlling devices connected together via an inlet supply line should be short, having regard to the unavoidable drop in pressure in the line, since the filling time would otherwise be unacceptably long;
batteries ranging in size from only a few cells up to several hundred cells; it is necessary in the case of the larger batteries, in view of the risk of leakage currents, for these to be divided up into an appropriate number of cell groups, to which the water supply is provided via separate lines.
Previously disclosed in GB No. 1 142 633 is a filling system which makes use of a storage container positioned beneath the outlet level of the level-controlling devices installed in the cells. The water is conveyed from the storage container by means of a pump either directly to the level-controlling devices or indirectly to these via a reservoir positioned at a higher level with a gravity feed to the cells. Any surplus water is returned by gravity to the storage container positioned at a lower level. The arrangement requires the availability of a mains electricty supply and is unsuitable for multi-cell batteries, for which a number of separate water supply branches are necessary.
A similar arrangement is disclosed in GB No. 2 041 629, which differs from the arrangement described above essentially in that water from a storage container is sucked into the level-controlling devices by means of a pump attached to the storage container.
This system suffers from the same disadvantages as the system disclosed in GB No. 1 142 633. Furthermore, negative pressure can be created which may damage the cells. By introducing a filling container in series between the storage container and the cells at a height such that the fluid levels in the filling container and the cells are essentially identical, it is possible to avoid harmful negative pressure, as may be appreciated from SE No. 7910526-8. This arrangement makes use of a central reserve of battery fluid, from which a pump conveys fluid to the aforementioned filling container on the cells. The fluid is sucked from here to the cells by the level-controlling devices, and any surplus is returned to the storage container. This complicated arrangement is suitable only for the filling of batteries with relatively few cells positioned on the same plane.
Contrastingly simple is an arrangement described in DE No. 23 03 244, in which cells with level-controlling devices are supplied with water by gravity from a storage containerpositioned above the electrolyte level of the cells. In spite of its simplicity this principle is not applicable to multi-cell batteries, in which the necessary level vessels would result in an installation which is difficult to monitor and onerous to maintain.
Previously disclosed systems, such as those mentioned above, may be well suited to certain applications, although they lack the necessary flexibility for them to be able to satisfy the fluctuating demands which may be placed on a filling arrangement in accordance with the above list of demands, the purpose of which is to achieve reduced maintenance costs through lower servicing requirements and/or rapid servicing of the battery installations, yet retaining high operational reliability in conjunction with a low cost for the arrangement and the installation.